collapse_expand_tree.py

import toga

class StartApp(toga.App):
    def startup(self):
        # Main window
        self.main_window = toga.MainWindow(self.name)
        self.main_window.app = self

        # Tree widget from Toga
        self.tree = toga.Tree(['Navigate'])

        # Insert nodes top level on the tree
        self.tree.insert('root1')
        self.tree.insert('root2')

        # Insert node with the children expanded
        #   Informs if a node is collapsed in the args of the insert method
        self.r3 = self.tree.insert('root3', collapsed=False)
        self.sub_r3 = self.tree.insert('sub_r3', self.r3)
        # Informs that a node is expanded using a method call
        self.sub_r3.expand()
        self.tree.insert('sub_sub_r3', self.sub_r3)

        # Update the tree layout
        self.tree.apply_layout()

        # Buttons to interact with the tree and update the tree visualization
        update_tree_button_collapse = toga.Button('Collapse root3',
                                        on_press=self.callbackCollapse)
        update_tree_button_expand = toga.Button('Expand root3',
                                        on_press=self.callbackExpand)
        self.control_box = toga.Box(children=[update_tree_button_collapse,
                                                update_tree_button_expand])

        # Main widget of the application, show both the Tree data and the
        #   buttons to control thee application
        frame = toga.SplitContainer()
        frame.content = [self.tree, self.control_box]

        # Add the main widget inside of the main application
        self.main_window.content = frame
        # Show the application
        self.main_window.show()

    def callbackCollapse(self, event):
        # Collapse the node using a method call
        self.r3.collapse()
        # Update the tree layout
        self.tree.apply_layout()

    def callbackExpand(self, event):
        # Expand the node using a method call
        self.r3.expand()
        # Update the tree layout
        self.tree.apply_layout()

def main():
    # Start the application with the title and the name of the organization
    app = StartApp('Test Tree, expand and collapse features',
                    'org.pybee.test')
    app.main_loop()

if __name__ == '__main__':
    main()